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0.1. LARMORE.

POSITIVE TIMER FOR LOCK STITCH SEWING MACHINES.

APPLICATION FILED AUG.10, 1918.

1,325,020. Y Patented Dec. 16,1919.

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1,325,020. j Patented Dec.16,1919.

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0.1. LARMORE. POSITIVE HMER FOR LOCK STITCH SEWING MACHINES. APPLICATION FILED AUGJO, 1918.

1,325,020. Patented Dec. 16,1919.

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Specification of Letters Patent.

POSITIVE TIMER-FOR LOCK-STITCH SEWING-MACHINES.

Patented Dec. 1 19.19.

Application filed August 10, 1918. Serial No. 249,241

To all whom it may concern:

Be it known that I, OVILA J. LARMORE, a citizen of the United States, residing at WVappingers Falls, in the county of Dutchess and State of New York, have invented certain new and useful Improvements in Positive Timers for Lock-Stitch Sewing-Machines, of which the following is a specification.

This invention relates to those lock-stitch sewing machines employing an upper needle actuating shaft, a lower, loop-taker shaft, and a belt-drive connection between the said shafts.

The belt commonly used on such machines is either of leather, or, of hemp or cord strands and, after userfor a relatively short period of time, stretches through use, or, by reason of oil thrown thereon when the machine is in operation becomes unduly lengthened. This requires frequent removal and replacement of the belt used in this type of sewing machine, with incident loss of time of the operative and cost of upkeep. Furthermore, looseness of the belt soon destroys the accurate timing of the loop-taker shaft with the needle actuating shaft, allowing the loop-taker to shake back and forth, instead of rotating in perfect timing with the needle actuating shaft. As a result of looseness of the belt and this action of the loop-taker, stitches are skipped and threads are broken.

The well-known WillcoX & Gibbs and Singer sewing machines of the high-speed, lock-stitch type are subject to the foregoing troubles and it is the particular object of my invention to provide novel means which will insure accurate timing of the loop-taker with the needle in such machines. ,The invention, however, is adapted for use in connection with any sewing machine having the two shafts aforesaid and a belt drive connecting them.

My object is to provide novel means, cooperating with the belt of a high-speed, lock-stitch sewing machine for the purpose of insuring positive timing of the upper and lower shafts and, hence, of the needle and the loop-taker, to the end that broken threads, skipped stitches, and other defects due to looseness of the belt connecting said shafts, will be obviated, and the substitution of a new belt for one that has stretched from any cause will be unnecessary. My invention not only. saves time otherwise lost in taking out a loose or stretched belt and p putting in a new one but it enables a stretched belt to be used until worn out, thus saving expense.

The present invention requires no modification of the belt drive as now used on high-speed lock-stitch sewing machines but comprises novel means applicable to any machine of that class, adapted to take up slack in the belt and to insure positive timing of the loop-taker shaft and the needle actuating shaft. The device is adapted for adjustment from time to time to compensate for further slack in the belt and enables the belt to be used untilit is worn out without necessitating removal of the belt from the sewing machine.

The embodiment of the invention hereinafter described and which is disclosed in the accompanying drawings is subject to modification and is to be considered as illustrative, instead of restrictive, of the scope of the invention. I

In the accompanying drawings:

Figure 1 is a side elevation, partly broken away, of a high-speed, lock-stitch sewing machine equipped with my invention;

Fig. 2, is a vertical section on the line 2-2, Fig. 1;

Fig. 3, is a bottom view of the right-hand end of the machine of Fig. 1; i Y

Fig. 4:,is a detail side elevation, partly in section, of the timer by itself;

Fig. 5, is a detail rear elevation thereof; liig. 6, is a detail bottom view thereof; anc

Figs. 7 and 8 detail views showing how the timer maybe applied to another kind of sewing machine drive belt.

In Figs. 1, 2, 3, the invention is shown applied to the well-known Willcox & Gibbs highspeed lock-stitch sewing machine, so much of the machine being illustrated as will disclose the nature of the invention; it

I is to be understood, however, that the invention is applicable to any sewing machine having a belt drive between the upper needle-actuating shaft and the lower looptaker shaft.

The bed-plate appears at 1, the arm at 2 and the hollow pillar at 3. The upper, needle-actuating shaft 1 drives the needle 5 and is provided with the usual pulley 6 and balance wheel 7. The lower shaft 8 is journaled in suitable bearings below the bed-plate 1 and carries the usual loop-taker 9 which, in cooperation with the needle 5, forms the lock-stitch. The feed is operated by the rock-shafts 10, 11, which are operatively connected to'the shaft 4 by connecting rods 12, 13.

Fast on shafts 1 and 8, respectively, are the sprockets or pin-wheels 1e, 15 which are connected by an endless belt 16 having perforations 17 that receive the pins or teeth on the wheels 1%, 15. The common practice is to use a light leather belt 16 and to reinforce the perforations 17 with metallic eyelets. The object of the direct bildrive thus provided is to positively revo. the shaft 8 in perfect timing with the shart 4 from which it is driven, thereby causing; the loop-taker 9 to so perfectly coordinate with the needle 5 that a perfect lock-stitch will result.

In practice, however, such perfect timing does not result from this belt-drive. The belt stretches from use, which is greatly increased by its being subject to oil thrown thereon by the moving parts of the ma chine. Consequently, undue stretching of the belt 16 soon causes the holes 17 to not: and then skip the pins of the wheels l l, 15, thus destroying the timing of the needle 5 and loop-taker 9, resultin in skipped stitches and broken threads. A new belt must then be substituted for the one in use, which requires considerable time and involves the cost of the new belt and loss of the old one which is not worn out and. yet has to be discarded because its usefulness has ended.

To remedy the foregoing difficulty and expense, I have devised novel, adjustable means cooperating with the belt 16 by which slack therein is taken up and positive timing of the needle and loop-taker insured. The invention is shown detached in Figs. 4, 5, 6 and applied to the sewing machine in Figs. 1, 2, 3.

Referring first to Figs. 4., 5, 6,

the base plate 18 is provided with holes 19 to receive machine screws 20 (Fig-s. 2-, 3) for attacl the device to the underside of the bcdp- 1. Suitably fastened to the base plate 18 is a hinge 21 to which, in turn, is fastened. as at 22, one part 23 of an angular arm which has a screwclamp 25 for adjust blv securing one end of a pintle or stub-shalt 2-6 on which is journaled a roller 27. The part 23 has a hole 28 through which loosely passes a tension screw 29 which has its end engaged with a screw-threaded hole 30 in base plate 18; a coil spring 31 sinrounds the shank of screw 29 between the part and the head of the screw and tends to force the part 23 toward the base plate 18. Two screws 32, which engage screw -threaded holes in the part 23,have their tips bearing on the base plate 18 at 33. These screws may be turned to adjust the arm 24, and hence the roller 27 as may be desired. The spring 31 keeps the tips of the screws 32 against the base plate 18 at all times but yields, or expands, as the case may be, when the screws 32 are adjusted.

The positive timer described is applied to the bed plate 1, and cooperates with the belt 16, in the manner shown in Figs. 1, 2, 3. The base plate 18 is so positioned, and secured by the machine screws 20, that the arm 24: extends up within the hollow pillar 3, the roller 2'? bearing on one stretch of the belt 16. By suitably adjusting the screws 32 the roller 27 will bear with the proper pressure on the belt 16 to insure that every perforation 17 receive a pin or tooth of the wheels 1 1-, 15. Consequently, the lower shaft 8 will be rotated in perfect timing with the upper shaft 4: and the needle 5 will correctly cooperate with the looptaker 9 to insure the formation of perfect lock-stitches at all times.

As the belt 16 stretches from use, the screws 32 may be quickly and easily turned by a screw driver without necessitating any other adjustment to compensate for the slack. The belt does not have to be removed, as has heretofore been necessary when the belt stretched and the timing was destroyed, and the effective life of tie belt is greatly increased.

The Singer machine employs belt composed of parallel cords connected together by transverse clips as shown at 34, Figs. 7 and 8, for driving the lower shaft 8 from the upper shaft 4. The belt runs over wheels 35, 36 which have notches or grooves 37 to receive the clips 3st. My invention may be applied to this type of belt, so as to be used on the Singer machine, by sub stituting for the roller 27, a roller haw i-ng; notches or grooves 39.

iv hat I claim is:

A self-contained belt-tightener, dapted to be attached to a sewin machine for cooperating with the belt which connects the needle-actuating shaft and the loop-taker operating shaft to insure positive timing of the shafts aforesaid, comprising a base plate, an arm hinged thereto, a roller carried by the arm and adapted to bear on the belt, a screw threaded through the arm and having its tip bearing on the base plate, a screw engaged with the base plate and passing loosely through the arm, and a spring cooperating with said last-named screw and with the arm.

In testimony whereof I affix mv signature.

:OVILA J. LARMGRE. 

